It depicts instances of the first types of bad human behavior (such as saying "I need a vacation from my vacation", growing dreadlocks and calling ultimate frisbee "ultimate", and a waiter addressing a diner's empty plate with "I guess you hated it") and explanations of the tortures they earned, as well as models of the punishments (such as a cheese grater and a penis flattener).
The examples likely come from the Accounting Department, which records all new actions to assign value toward them.
Most of the behavior in the Museum (with a few exceptions) falls into the 1% of new actions that are not Weird Sex Things.
The Museum also contains robotic models of the human performing the actions that earned their spot in The Bad Place (with exception of the residents of Michael's Neighborhood, who exhibit their personalities, simultaneously explaining their faults and the manner in which they are tortured, as is the premise of Michael's neighborhood experiment).
Michael states that the museum is an unpopular location and that few ever enter. It is possible that every time there is a new exhibit, there is a party in the Museum, as there was with Michael's neighborhood, or perhaps that was only because the experiment would change the very manner in which The Bad Place operated.